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<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<script type="text/javascript">
		var n1=2;
		var n2=3;
		 n1+=n2;   //等价于n1=n1+n2;
		 alert(n1);


	</script>
</head>
<body>
	
</body>
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